content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  package io.reactivex.flowable.processors;
  
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.common.RxJavaCommonPlugins;
  import io.reactivex.common.annotations.*;
  import io.reactivex.common.exceptions.MissingBackpressureException;
  import io.reactivex.flowable.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.flowable.internal.utils.BackpressureHelper;
  
  /**
   * Processor that multicasts all subsequently observed items to its current {@link Subscriber}s.
   *
   * <p>
   * <img width="640" height="405" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/S.PublishSubject.png" alt="">
   *
   * <p>The processor does not coordinate backpressure for its subscribers and implements a weaker onSubscribe which
   * calls requests Long.MAX_VALUE from the incoming Subscriptions. This makes it possible to subscribe the PublishProcessor
   * to multiple sources (note on serialization though) unlike the standard Subscriber contract. Child subscribers, however, are not overflown but receive an
   * IllegalStateException in case their requested amount is zero.
   *
   * <p>The implementation of onXXX methods are technically thread-safe but non-serialized calls
   * to them may lead to undefined state in the currently subscribed Subscribers.
   *
   * <p>Due to the nature Flowables are constructed, the PublishProcessor can't be instantiated through
   * {@code new} but must be created via the {@link #create()} method.
   *
   * Example usage:
   * <pre> {@code
  
    PublishProcessor<Object> processor = PublishProcessor.create();
    // subscriber1 will receive all onNext and onComplete events
    processor.subscribe(subscriber1);
    processor.onNext("one");
    processor.onNext("two");
    // subscriber2 will only receive "three" and onComplete
    processor.subscribe(subscriber2);
    processor.onNext("three");
    processor.onComplete();
  
    } </pre>
   * @param <T> the value type multicasted to Subscribers.
   */
  public final class PublishProcessor<T> extends FlowableProcessor<T> {
      /** The terminated indicator for the subscribers array. */
      @SuppressWarnings("rawtypes")
      static final PublishSubscription[] TERMINATED = new PublishSubscription[0];
      /** An empty subscribers array to avoid allocating it all the time. */
      @SuppressWarnings("rawtypes")
      static final PublishSubscription[] EMPTY = new PublishSubscription[0];
  
      /** The array of currently subscribed subscribers. */
      final AtomicReference<PublishSubscription<T>[]> subscribers;
  
      /** The error, write before terminating and read after checking subscribers. */
      Throwable error;
  
      /**
       * Constructs a PublishProcessor.
       * @param <T> the value type
       * @return the new PublishProcessor
       */
      @CheckReturnValue
      public static <T> PublishProcessor<T> create() {
          return new PublishProcessor<T>();
      }
  
      /**
       * Constructs a PublishProcessor.
       * @since 2.0
       */
      @SuppressWarnings("unchecked")
      PublishProcessor() {
          subscribers = new AtomicReference<PublishSubscription<T>[]>(EMPTY);
      }
  
  
      @Override
      public void subscribeActual(Subscriber<? super T> t) {
          PublishSubscription<T> ps = new PublishSubscription<T>(t, this);
          t.onSubscribe(ps);
          if (add(ps)) {
              // if cancellation happened while a successful add, the remove() didn't work
              // so we need to do it again
              if (ps.isCancelled()) {
                  remove(ps);
              }
          } else {
              Throwable ex = error;
              if (ex != null) {
                  t.onError(ex);
              } else {
                  t.onComplete();
              }
          }
      }
  
      /**
       * Tries to add the given subscriber to the subscribers array atomically
       * or returns false if the subject has terminated.
       * @param ps the subscriber to add
       * @return true if successful, false if the subject has terminated
       */
      boolean add(PublishSubscription<T> ps) {
          for (;;) {
              PublishSubscription<T>[] a = subscribers.get();
              if (a == TERMINATED) {
                  return false;
              }
  
              int n = a.length;
              @SuppressWarnings("unchecked")
              PublishSubscription<T>[] b = new PublishSubscription[n + 1];
              System.arraycopy(a, 0, b, 0, n);
              b[n] = ps;
  
              if (subscribers.compareAndSet(a, b)) {
                  return true;
              }
          }
      }
  
      /**
       * Atomically removes the given subscriber if it is subscribed to the subject.
       * @param ps the subject to remove
       */
      @SuppressWarnings("unchecked")
      void remove(PublishSubscription<T> ps) {
          for (;;) {
              PublishSubscription<T>[] a = subscribers.get();
              if (a == TERMINATED || a == EMPTY) {
                  return;
              }
  
              int n = a.length;
              int j = -1;
              for (int i = 0; i < n; i++) {
                  if (a[i] == ps) {
                      j = i;
                      break;
                  }
              }
  
              if (j < 0) {
                  return;
              }
  
              PublishSubscription<T>[] b;
  
              if (n == 1) {
                  b = EMPTY;
              } else {
                  b = new PublishSubscription[n - 1];
                  System.arraycopy(a, 0, b, 0, j);
                  System.arraycopy(a, j + 1, b, j, n - j - 1);
              }
              if (subscribers.compareAndSet(a, b)) {
                  return;
              }
          }
      }
  
      @Override
      public void onSubscribe(Subscription s) {
          if (subscribers.get() == TERMINATED) {
              s.cancel();
              return;
          }
          // PublishSubject doesn't bother with request coordination.
          s.request(Long.MAX_VALUE);
      }
  
      @Override
      public void onNext(T t) {
          if (subscribers.get() == TERMINATED) {
              return;
          }
          if (t == null) {
              onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
              return;
          }
          for (PublishSubscription<T> s : subscribers.get()) {
              s.onNext(t);
          }
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public void onError(Throwable t) {
          if (subscribers.get() == TERMINATED) {
              RxJavaCommonPlugins.onError(t);
              return;
          }
          if (t == null) {
              t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
          }
          error = t;
  
          for (PublishSubscription<T> s : subscribers.getAndSet(TERMINATED)) {
              s.onError(t);
          }
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public void onComplete() {
          if (subscribers.get() == TERMINATED) {
              return;
          }
          for (PublishSubscription<T> s : subscribers.getAndSet(TERMINATED)) {
              s.onComplete();
          }
      }
  
      /**
       * Tries to emit the item to all currently subscribed Subscribers if all of them
       * has requested some value, returns false otherwise.
       * <p>
       * This method should be called in a sequential manner just like the onXXX methods
       * of the PublishProcessor.
       * <p>
       * Calling with null will terminate the PublishProcessor and a NullPointerException
       * is signalled to the Subscribers.
       * <p>History: 2.0.8 - experimental
       * @param t the item to emit, not null
       * @return true if the item was emitted to all Subscribers
       * @since 2.1
       */
      public boolean offer(T t) {
          if (t == null) {
              onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
              return true;
          }
          PublishSubscription<T>[] array = subscribers.get();
  
          for (PublishSubscription<T> s : array) {
              if (s.isFull()) {
                  return false;
              }
          }
  
          for (PublishSubscription<T> s : array) {
              s.onNext(t);
          }
          return true;
      }
  
      @Override
      public boolean hasSubscribers() {
          return subscribers.get().length != 0;
      }
  
      @Override
      public Throwable getThrowable() {
          if (subscribers.get() == TERMINATED) {
              return error;
          }
          return null;
      }
  
      @Override
      public boolean hasThrowable() {
          return subscribers.get() == TERMINATED && error != null;
      }
  
      @Override
      public boolean hasComplete() {
          return subscribers.get() == TERMINATED && error == null;
      }
  
      /**
       * Wraps the actual subscriber, tracks its requests and makes cancellation
       * to remove itself from the current subscribers array.
       *
       * @param <T> the value type
       */
      static final class PublishSubscription<T> extends AtomicLong implements Subscription {
  
          private static final long serialVersionUID = 3562861878281475070L;
          /** The actual subscriber. */
          final Subscriber<? super T> actual;
          /** The subject state. */
          final PublishProcessor<T> parent;
  
          /**
           * Constructs a PublishSubscriber, wraps the actual subscriber and the state.
           * @param actual the actual subscriber
           * @param parent the parent PublishProcessor
           */
          PublishSubscription(Subscriber<? super T> actual, PublishProcessor<T> parent) {
              this.actual = actual;
              this.parent = parent;
          }
  
          public void onNext(T t) {
              long r = get();
              if (r == Long.MIN_VALUE) {
                  return;
              }
              if (r != 0L) {
                  actual.onNext(t);
                  if (r != Long.MAX_VALUE) {
                      decrementAndGet();
                  }
              } else {
                  cancel();
                  actual.onError(new MissingBackpressureException("Could not emit value due to lack of requests"));
              }
          }
  
          public void onError(Throwable t) {
              if (get() != Long.MIN_VALUE) {
                  actual.onError(t);
              } else {
                  RxJavaCommonPlugins.onError(t);
              }
          }
  
          public void onComplete() {
              if (get() != Long.MIN_VALUE) {
                  actual.onComplete();
              }
          }
  
          @Override
          public void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  BackpressureHelper.addCancel(this, n);
              }
          }
  
          @Override
          public void cancel() {
              if (getAndSet(Long.MIN_VALUE) != Long.MIN_VALUE) {
                  parent.remove(this);
              }
          }
  
          public boolean isCancelled() {
              return get() == Long.MIN_VALUE;
          }
  
          boolean isFull() {
              return get() == 0L;
          }
      }
  }
  